Relativistic scalar and spin–orbit density functional calculations of the electronic structure, NICS index and ELF function of the [Re2(CO)8(μ-BiPh)2] and [Re2(CO)8(μ-BiPh2)2] clusters

Abstract

Abstract Relativistic scalar and spin–orbit density functional calculations of the electronic structure, Nucleus-Independent Chemical Shift (NICS) index and ELF function of the [Re 2 (CO) 8 (μ-BiPh) 2 ] and [Re 2 (CO) 8 (μ-BiPh 2 ) 2 ] clusters are reported. We show here that the [Re 2 (CO) 8 (μ-BiPh) 2 ] cluster has large negative NICS values in the region defined by the Re–Bi–Re–Bi four-membered ring and the ELF function shows significant electron delocalization density in the center of the metallic ring, thus indicating an aromatic cluster. In contrast the Re–Bi–Re–Bi four-membered ring in the [Re 2 (CO) 8 (μ-BiPh 2 ) 2 ] cluster has negligible paratropic ring currents and the ELF function shows a low-density region within the metallic ring indicating that aromaticity is switched off. However, the phenyl ligands in both clusters show the expected aromatic character.